The 2012 London summit on family planning was convened to shine light on the fundamental role that contraception has to play in reducing infant mortality, improving women's health, tackling household poverty, increasing school enrolment … the list goes on.

A basic flaw in the millennium development goals (MDGs) established in 2000 was the failure to include sexual and reproductive health and rights (SRHR). Access to contraception wasn't even a consideration until 2005, and wasn't incorporated into the MDGs until 2007. It meant that a proven strategy for improving health and reducing poverty was absent from development efforts for almost a decade.

This collective failure to prioritise SRHR has hindered the progress of many of the other MDGs, and has taken a great human toll. To add insult to injury, this late inclusion meant that investment in family planning programmes plummeted (pdf) between 1995 and 2007 by 65% – from $980m to $340m.

The decline is even more significant when you take account of the increasing need for contraception from the growing numbers of adolescents whose needs are often forgotten – or deliberately ignored.

The maths has already been done; meeting the need for contraceptives for all women in the developing world would cost $8.1bn annually – double the current level of expenditure. But the impact of this additional investment would be incredible.

Serving women in the developing world who want to delay, space or limit their pregnancies but aren't using modern contraception would prevent 54m unintended pregnancies, including 21m unplanned births; 26m abortions (of which 16m would be unsafe); 7m miscarriages; 79,000 maternal deaths; and 1.1m infant deaths.

The summit responded ambitiously – generating significant policy, financing and delivery commitments from developing country governments, backed by $2.6bn from donors and creating a seven-year global coalition of governments, civil society and the private sector. It laid the foundations for the family planning agenda and the formation of the Family Planning 2020 taskforce (FP2020).

The summit was only the first part of the equation. FP2020 will ensure sustained international momentum, advocacy and accountability. The real test of the summit will be how these commitments translate into country-led actions. And ultimately, whether a young woman in Niger or an older mother in Afghanistan is able to determine freely and for herself whether to have children, or when and how many, and is able to access the information, services and supplies needed.

This is an unprecedented opportunity to secure a world of justice, choice and wellbeing for all. The International Planned Parenthood Federation, a global movement, galvanised more than 1,300 civil society organisations to express, with one united voice, a commitment to the summit's ambition.

Put simply: no one should be denied the same choices that many take for granted. It's about allowing women and girls to make their own choices about their bodies. We know that when women are able to choose, they choose more for their children, not more children.

Access to contraception must be seen as part of wider efforts on health and equity. That means addressing early and forced marriages, preventing early pregnancy, increasing access to safe abortion, ending female genital mutilation, discrimination and sexual violence, improving maternal health, reducing HIV transmission, and increasing participation in education.

Improving women's and children's health and wellbeing is central to creating more prosperous families, communities and nations.

If we achieve the summit goal of enabling an additional 120 million women in the poorest countries to have access to contraception by 2020, it would be an achievement all of us in this field would be proud of.

•Julia Bunting is programmes and technical director at the International Planned Parenthood Federation